| Recent hydrogeological events have increased both public interest and that
of the Scientific Community in a more accurate study of flooding in urban
areas. The present project proposes a new model which offers an optimal
integration of two models, one for flood wave propagation in riverbeds and
the other for flooding in urban areas.
We consider it necessary to not only treat the modelling of the outflow in
riverbeds and outside riverbeds.together but to integrate them thoroughly.
We simulate the propagation in riverbed of the flood event with a model
solving the equations of De Saint Venant with the explicit scheme at the
finite differences by McCormack. The propagation outside the riverbed is
simulated using an algorithm proposed by Braschi et al. (1990).
This algorithm is based on a local discretization of the urban territory,
divided in a series of "tanks" and "channels". Each tank is associated
with an area of an extension related to the position of the other tanks and
the quantity of buildings, modelled as insurmountable obstacles.
The model facilitates the simultaneous performance of the two simulations: at
each instant, the quantitiy of water overflow, depending on the piezometric
level in every section, is calculated as a function of the dimensions of the
weirs (the banks), assuming it passes through the critical state. Then, it
is transferred to the tanks placed in the surroundings of the overflow
points. Those points are the starting nodes for the propagation of the flood
because they are connected to the network of tanks in which the surrounding
land has been schematised.
In this paper, we present a comparison of one of the most powerful models of
inundation simulation in urban and no-urban areas. The field area is the
city of Albenga (SV, Italy) and the simulated event is the inundation of the
1994 (return period of about 25 years). |